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26,176 ÷ 4 = 6,544
Thus, the maximum number of XP Snapshot pairs that can be created is 6,544.
Calculating the Number of XP Snapshot Pairs by Using the Shared Memory Capacity for the Virtual
Volume Management Area
The V-VOL management area consists of the following three elements:
• Pool association information
• Pool management block
• Management information other than those above (shared memory is fixed to 10 MB)
The shared memory of the V-VOL management area differs according to the additional shared
memory. Table 17 (page 37) shows the detailed information.
Table 17 Additional Shared Memory for the V-VOL Management Area
Shared Memory CapacityShared Memory
751,619,276 bytesXP Snapshot 1
1,073,741,823 bytesXP Snapshot 2
2,147,483,647 bytesXP Snapshot 3
3,221,159,935 bytesXP Snapshot 4
4,294,901,759 bytesXP Snapshot 5
To calculate the maximum number of XP Snapshot pairs that can be created for a subsystem, use
the following formula:
Maximum number of XP Snapshot pairs = Total capacity of P-VOLs ÷
{ (Capacity of one P-VOL ÷ 524,288) × 524,288}
524,288: Unit by which pool association information manages the capacity of a P-VOL (in kilobytes)
You must round up the value enclosed by the two upward arrows (↑) to the nearest whole number.
NOTE: Pool association information manages the P-VOL capacity by 524,288 KB.
To calculate the total capacity of P-VOLs, use the following formula:
Total capacity of P-VOLs = (S1 ÷ 8,736) × 2,048 × 256
S1: Shared memory capacity for pool association information (in bytes)
8,736: Capacity of pool association information per one table (in bytes)
2,048: Number of slots of the P-VOL which can be managed by the pool association information
for one table
256: Capacity of one slot (in kilobytes)
Note that you must round up the value enclosed by the two upward arrows (↑) to the nearest whole
number.
To calculate S1 (shared memory capacity for pool association information), use the following
formula:
S1 = S − S2 - 10,485,760
S: Shared memory capacity for the whole V-VOL management area (in bytes)
S2: Shared memory capacity for the pool management block (in bytes)
10,485,760: Fixed management information (in bytes)
Operational Requirements 37